1. Field of the Invention
The present invention relates to a vacuum system used for an automotive vehicle, and more specifically to a check valve used with a vacuum system including a vacuum brake booster and another vacuum actuator (such actuator as used for a vacuum clutch booster) such that it is possible to prevent vacuum pressure (negative pressure) within the vacuum system from being reduced, in case where a trouble with airtightness occurs in the vacuum clutch booster; that is, it is possible to assure the function of the vacuum brake booster which is crucially important for safety.
2. Description of the Prior Art
In a prior-art vacuum system used with an automotive vehicle which comprises an engine intake manifold as a vacuum generator, a vacuum brake booster, a vacuum clutch booster, a first check valve, and a second check valve, when the vacuum clutch booster is defective with respect to airtightness, since the vacuum pressure at the vacuum generator drops, and the vacuum brake booster loses vacuum pressure each time it is actuated, soon the vacuum brake booster does not function effectively and an unusually great brake depressing force is required. In order to overcome this problem, a throttle is provided between the intake manifold and the second check valve and an additional vacuum tank is provided between the second check valve and the vacuum clutch booster, thus resulting in higher cost and larger engine volume.
A more detailed description of the prior-art vacuum system used with an automotive vehicle will be made hereinbelow with reference to the attached drawings under DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS.